This thesis describes the language of the Huli speech community of the Southern Highlands of Papua New Guinea. The first chapter situates the speech community in its historical setting, and refers to previous, mainly non-linguistic, studies. The second chapter situates the commuity in its geographical and 'traditional' setting, recording putative migrations and dialectal variations. The third chapter describes segmental phonology at a level of detail not previously given in accounts of the language, while the fourth chapter presents a tentative exploration of prosodic features. The fifth chapter describes verbs, the sixth adverbials, and the seventh nominals: in each instance there is an emphasis on morphology and morphophonemic processes hitherto unrecorded for Huli. The eighth chapter describes word complexes, and the ninth group complexes, using a systemic-functional approach that establishes a descriptive framework that indicates useful insights into the pragmatics of the language. Chapter ten selects and explores, in varying degrees, semantic features that are typologically interesting, while chapter eleven re-focusses the thesis on sociolinguistic issues. The twelveth chapter presents a dozen texts, which it interprets and comments on in the light of linguistic and sociological descriptions presented previously. The appendices that follow give the data bases for some of the descriptions given in the thesis body. The body of the thesis is concerned with describing the language as it is being created and used by living, real, people. Hence, the language forms at each level are described and interpreted in relation to their functions in creating meaning. This has necessitated presenting in some detail phonological and morphological data that need to be described if the language is to be seen as the growing, changing expression of the living society that uses and creates it.